Not applicable
This invention relates to a print head assembly. More particularly, this invention relates to a print head assembly and to a method of assembling a print head.
The Applicant has developed a page width ink jet print head that is the subject of a large number of United States patents and patent applications. The print head is capable of printing text and images having resolutions as high as 1600 dpi.
An integral part of the print head is one or more print head chips. The print head chips are the product of an integrated circuit fabrication technique. In particular, each print head chip comprises a plurality of nozzle arrangements that are positioned along a length of silicon wafer substrate. Each nozzle arrangement is in the form of a micro electro-mechanical system. The applicant has developed technology that allows for the fabrication of such print heads having up to 84,000 nozzle arrangements.
In general, during assembly of a print head, the print head chips are positioned in some form of carrier. The carrier forms part of an ink distribution arrangement such as an ink distribution manifold. Instead, the carrier can itself be attached in some way to an ink distribution arrangement to define some form of interface between the print head chips and the ink distribution arrangement.
The positioning of the print head chips in their respective carriers usually takes place by way of simply urging the print head chip into a recess defined in the carrier. The recess is thus dimensioned so that the fit is a snug fit or an interference fit to ensure that the print head chip is retained in position in the carrier.
Due to the elongate nature of the print head chip, the print head chip is susceptible to flexure. As a result, any stresses that are exerted on the carrier during normal handling and operation can result in flexure of the carrier and thus the print head chip. It will be appreciated by those of ordinary skill in the art that the fact that the nozzle arrangements are each in the form of a micro electro-mechanical system makes such flexure highly undesirable.
A particular problem with such a fit stems from the possible ingress of particulate matter into the recess. This is especially so if the matter is in the form of one or more relatively hard particles. When the chip is urged into the recess, such a particle can become sandwiched between the print head chip and a wall of the recess. This results in a region of stress concentration at that point on the print head chip that is impinged upon by the particle. Thus, when the chip is subjected to a small amount of flexure that would usually not cause a problem, the stress concentration can cause a fracturing of the print head chip.
The Applicant has conceived the present invention to address this problem and to alleviate the necessity for the print head manufacturer to achieve a particulate free environment for the assembly stage of the print head. As is well known, chip manufacturers incur substantial expense to ensure that chip fabrication environments are kept sterile. Applicant believes that it is desirable that the need for such sterile environments does not extend to the print head assembly stage.
According to a first aspect of the invention, there is provided an ink jet print head assembly that comprises
at least one elongate ink jet print head chip that is the product of an integrated circuit fabrication technique;
at least one corresponding ink jet print head chip carrier that defines an elongate recess having a pair of opposed side walls, the, or each, print head chip being received in one respective recess, the, or each, ink jet print head chip and said respective recess being dimensioned so that a gap is defined between the, or each, ink jet print head chip and each side wall; and
resiliently deformable material that is positioned in each gap to retain the, or each, print head chip in position in said respective recess.
According to a second aspect of the invention, there is provided a method of assembling an ink jet print head having at least one elongate ink jet print head chip that is the product of an integrated circuit fabrication technique and at least one corresponding ink jet print head chip carrier that defines an elongate recess having a pair of opposed side walls, the, or each, ink jet print head chip and said respective recess being dimensioned so that a width of said the, or each, print head chip is less than a width of said respective recess to a predetermined extent, the method comprising the steps of:
positioning the, or each, ink jet print head chip in said respective carrier so that a gap is defined on each side of the ink jet print head chip by said pair of opposed side walls and the ink jet print head chip; and
at least partially filling each gap with an adhesive that is selected from a group of adhesives that cure into elastically deformable material to fix the, or each, ink jet print head chip in said respective recess.